Method for testing memory device

ABSTRACT

Disclosed is a method for testing a memory device, which can test a memory cell block while testing another memory cell block, so as to catch a process defect of the memory device within a short time period, thereby reducing the test time. The method for testing a memory device provided with a bank including N memory cell blocks and sense amplifiers, the method comprising the steps of: a) expressing the N memory cell blocks as a first, a second, . . . , an Nth memory cell block; b) sequentially activating odd-numbered memory cell blocks of the N memory cell blocks one by one in a predetermined time period; c) performing sense, read (or write) and precharge operations for each activated memory cell block; and d) performing steps a) to c) for even-numbered memory cell blocks after tests for all the odd-numbered memory cell blocks are finished.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for testing a memory device,and more particularly to a method for detecting a process defect of amemory device within a short period of time.

2. Description of the Prior Art

As generally known in the art, a memory device includes a memory bankfor storing data, a row circuit unit and a column circuit unit forreading/writing data from/to the memory bank, and an input/output unitfor inputting/outputting data.

From among these components, the memory bank including a plurality ofmemory cell arrays performs a very important function in the memorydevice. However, a leakage current may be introduced into an unspecificbit line of the memory band due to a process defect, so that cell faultmay occur due to the leakage current.

Therefore, a manufacturer screens various failures in the memory bankthrough several steps and various methods. As a result of the screen,when a cell having a defect is detected, the cell is replaced with aredundancy circuit.

A memory bank includes a plurality of memory cell blocks (see FIG. 1 forthe construction of a memory bank), and the memory cell blocks aresequentially tested. That is, after the test for a first memory cellblock has been finished, the test for a second memory cell block isperformed. After the test for the second memory cell block has beenfinished, the test for a third memory cell block is performed. In such amanner, the test is sequentially performed until the test for the lastmemory cell block has been completed.

However, in order to test one word line through active, write, andprecharge operations, several hundreds of μs to several ms may berequired. Therefore, the conventional test method has a problem in thata very long test time is required to detect a weak cell.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made to solve theabove-mentioned problems occurring in the prior art, and an object ofthe present invention is to provide a method capable of testing a memorycell block while testing another memory cell block, thereby reducingrequired test time.

In accordance with the present invention in order to accomplish theabove objects, there is provided a method for testing a memory deviceprovided with a bank which includes a plurality of memory cell blocks,the method comprising the steps of: a) activating one of the memory cellblocks and then activating other memory cell blocks one by one in apredetermined time period; and b) performing sense, read (or write) andprecharge operations for an activated memory cell block from among thememory cell blocks.

Herein, the active, sense, read and precharge operations are performedby commands applied from an exterior of the memory device.

Herein, the active, sense, read and precharge operations are performedsequentially for a plurality of word lines included in each of thememory cell blocks.

Herein, when sense, read (or write) and precharge operations for one ofthe memory cell blocks have been finished through step b), one ofremaining memory cell blocks is activated.

In accordance with the present invention, there is provided a method fortesting a memory device provided with a bank which includes N number ofmemory cell blocks and sense amplifiers located between the memory cellblocks, the method comprising the steps of: a) expressing the N memorycell blocks as a first, a second, . . . , an Nth (herein, ‘N’ is anatural number exceeding ‘three’) memory cell block; b) activating oneof odd-numbered (first, third, fifth, . . . ) memory cell blocks fromamong the N memory cell blocks, and then activating remainingodd-numbered memory cell blocks one by one in a predetermined timeperiod; c) performing sense, read (or write) and precharge operationsfor each activated memory cell block from among the odd-numbered memorycell blocks; and d) performing steps a) to c) for even-numbered memorycell blocks after tests for all the odd-numbered memory cell blocks havebeen finished.

Herein, the active, sense, read and precharge operations are performedsequentially for a plurality of word lines included in each of the Nmemory cell blocks.

Herein, when the sense, read (or write) and precharge operations for oneof the odd-numbered memory cell blocks have been finished through stepc), one of remaining odd-numbered memory cell blocks is activated; andwhen the sense, read (or write) and precharge operations for one of theeven-numbered memory cell blocks have been finished through step d), oneof remaining even-numbered memory cell blocks is activated.

In accordance with the present invention, there is provided a method fortesting a memory device provided with a bank which includes N number ofmemory cell blocks and sense amplifiers located between the memory cellblocks, the method comprising the steps of: a) expressing the N memorycell blocks as a first, a second, . . . , an Nth (herein, ‘N’ is anatural number exceeding ‘three’) memory cell block; b) activating oneof even-numbered (second, fourth, sixth, . . . ) memory cell blocks fromamong the N memory cell blocks, and then activating remainingeven-numbered memory cell blocks one by one in a predetermined timeperiod; c) performing sense, read (or write) and precharge operationsfor each activated memory cell block from among the even-numbered memorycell blocks; and d) performing steps a) to c) for odd-numbered (first,third, fifth, . . . ) memory cell blocks after tests for all theeven-numbered memory cell blocks have been finished.

Herein, the active, sense, read and precharge operations are performedsequentially for a plurality of word lines included in each of the Nmemory cell blocks.

Herein, when the sense, read (or write) and precharge operations for oneof the even-numbered memory cell blocks have been finished through stepc), one of remaining even-numbered memory cell blocks is activated; andwhen the sense, read (or write) and precharge operations for one of theodd-numbered memory cell blocks have been finished through step d), oneof remaining odd-numbered memory cell blocks is activated.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will be more apparent from the following detailed descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a block diagram illustrating a memory core unit to which amemory test method of the present invention is applied;

FIG. 2 is a detailed circuit of a cell matrix, a sense amplifier and asub-hole block shown in FIG. 1;

FIG. 3 is an internal timing diagram of a sense amplifier;

FIG. 4 is a write timing diagram; and

FIG. 5 is a read timing diagram.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a preferred embodiment of the present invention will bedescribed with reference to the accompanying drawings. In the followingdescription and drawings, the same reference numerals are used todesignate the same or similar components, and so repetition of thedescription on the same or similar components will be omitted.

FIG. 1 is a block diagram illustrating a memory core unit to which amemory test method of the present invention is applied. For reference,the memory core unit includes a memory bank for storing data and anadjacent part of the memory bank.

Referring to FIG. 1, the memory bank includes a plurality of memory cellblocks 110 to 117, each of which contains a plurality of cell matrixes.Herein, the cell matrix represents a cell array including a plurality ofmemory cells. For example, each cell matrix may be configured with512×256 bits. For reference, when there are eight memory cell blocks permemory bank and there are 512 word lines per memory cell block, a 9-bitrow address is required in order to select 512 word lines of one memorycell block, and a 3-bit address is required in order to select the eightmemory cell blocks.

Block control units 120 to 127 control signals relating to the wordlines of the memory cell blocks 110 to 117. That is, the block controlunits 120 to 127 enable or disable the word lines in response to anactive command or precharge command. As shown in FIG. 1, the blockcontrol units 120 to 127 are constructed to correspond one-to-one withthe memory cell blocks 110 to 117.

Sense amplifier control units 130 to 138 control signals relating to theoperation of sense amplifiers.

In a normal operation mode, the sense amplifier control units 130 to 138enable or precharge the sense amplifiers in response to an activecommand or precharge command.

Also, each of the sense amplifier control units 130 to 138 controls notonly signals ‘BISH’ and ‘BISL’ for controlling upper and lower bit lineisolation transistors to connect its corresponding memory cell block tothe corresponding sense amplifiers, but also relevant sub-hole blocks‘S/H’.

In a test mode, the sense amplifier control units 130 to 138 activate orprecharge the sense amplifiers based on a burst stop command orprecharge command. Also, each of the sense amplifier control units 130to 138 controls not only signals ‘BISH’ and ‘BISL’ for controlling upperand lower bit line isolation transistors to connect its correspondingmemory cell block to the corresponding sense amplifiers, but alsorelevant sub-hole blocks ‘S/H’.

In an active operation, the sense amplifier ‘S/A’ senses and amplifies afine voltage difference between a pair of bite lines ‘Bit’ and ‘/Bit’.

Each sub-word-line driver ‘SWLD’ functions to drive sub-word lines forcontrolling cell transistors, which are contained in, cell matrixeslocated at both sides of the relevant sub-word-line driver. In detail,when a sub-word line is enabled to a high level by a row address inresponse to an active command, the cell transistor connected to thesub-word line is enabled, and data stored in the cell transistor aretransferred to a corresponding bit line. Also, when a sub-word line isdisabled to a low level in response to a precharge command, the celltransistor connected to the sub-word line is disabled, and data storedin the cell transistor is maintained.

The sub-hole block ‘S/H’ includes main input/output lines ‘MIO’ and‘/MIO’, local input/output lines ‘LIO’ and ‘/LIO’, and block switchtransistors for connecting the main input/output lines and the localinput/output lines. The sub-hole block ‘S/H’ transfers data appliedthrough a data pin to a bit line during a write operation, and transfersdata of a bit line, which have been amplified by a sense amplifier, toan input/output data pad during a read operation.

FIG. 2 is a detailed circuit of a cell matrix, a sense amplifier and asub-hole block shown in FIG. 1. Herein, reference numerals ‘201’ and‘202’ represent cell matrixes, reference numeral ‘203’ represents asense amplifier, and number ‘204’ represents a sub-hole block. Inaddition, signal ‘RTO’ represents a restore signal, and signal ‘SE’represents a sense enable signal. The signals ‘RTO’ and ‘SE’ control thesensing operation of the sense amplifier.

Signal ‘BISH’ represents a ‘Bit Line Isolation High’ signal, andcontrols upper-side bit line isolation transistors of the senseamplifiers connected to a cell matrix.

Signal ‘BISL’ represents a ‘Bit Line Isolation Low’ signal, and controlslower-side bit line isolation transistors of the sense amplifiersconnected to a cell matrix.

Signal ‘VBLP’ represents a bit-line precharge voltage. ‘LIO’ and ‘/LIO’represent local input and output lines, and are connected between asense amplifier and main input/output lines ‘MIO’ and ‘/MIO’.

The ‘MIO’ and ‘/MIO’ represent main input and output lines. First endsof the main input/output lines are connected to the local input/outputlines, and second ends of the main input/output lines are connected to amain sense amplifier and a write driver (not shown). In a readoperation, read data are transferred to a data pin via bit lines, thelocal input/output lines and the main input/output lines. In contrast,in a write operation, write data are transferred to the bit lines viathe data pin, the main input/output lines and the local input/outputlines.

Signal ‘BLEQ’ represents a bit-line equalize signal.

In a normal operation mode, signal ‘BLEQ’ shifts to a low level when anactive command is applied to select a memory cell block, and signal‘BLEQ’ shifts to a high level when a precharge command is applied.

In a test mode, signal ‘BLEQ’ shifts to a low level when a memory cellblock is selected by a burst stop command while the memory is being inan active state, and signal ‘BLEQ’ shifts to a high level when aprecharge command is applied.

Signal ‘Yi’ represents an interior column address. When a read command(or a write command) is inputted while the memory is being in an activestate, an interior column address signal ‘Yi’ corresponding to anexterior column address applied from the exterior is enabled.Accordingly, , the local input/output lines ‘LIO’ and ‘/LIO’ areconnected to bit lines connected to the sense amplifier. As a result,data of bit lines, which have been amplified by the sense amplifier, areoutputted through the local input/output lines to the exterior.

Signal ‘/BLEQ’ represents the inverted signal of signal ‘BLEQ’, andcontrols the on/off operations of transistors which are connectedbetween the local input/output lines ‘LIO’ and ‘/LIO’ and the maininput/output lines ‘MIO’ and ‘/MIO’.

Signal ‘LIOPC’ represents a local input/output line precharge signal,and controls a transistor connected between the local input/output lines‘LIO’ and ‘/LIO’.

FIG. 3 is a view illustrating a test method according to an embodimentof the present invention, FIG. 4 is a view illustrating a writeoperation according to an embodiment of the present invention, and FIG.5 is a view illustrating a read operation according to an embodiment ofthe present invention.

Hereinafter, description will be made with reference to FIGS. 1 to 5 inrelation to a method for sequentially activating, sensing, writing (orreading) and precharging the odd-numbered memory cell blocks 111, 113,115 and 117 after sequentially activating, sensing, writing (or reading)and precharging the even-numbered memory cell blocks 110, 112, 114 and116 from among a plurality of memory cell blocks. For reference, themethod for sequentially testing odd-numbered memory cell blocks aftereven-numbered memory cell blocks have been sequentially tested is calledan ‘interleave’ test method or a ‘ping-pong’ test method.

A test mode starts when a test mode signal ‘TM’ is set to a high levelas shown in FIG. 3. For reference, in FIG. 3, reference numeral ‘110’represents a memory cell block 110, reference numeral ‘112’ represents amemory cell block 112, and reference numeral ‘114’ represents a memorycell block 114.

The following description will be given according to an applicationsequence of signals for testing a memory device.

1) Activation of Memory Cell Block 110:

When an active command ‘Act’ is inputted from the exterior together witha block address for appointing the memory cell block 110 and a rowaddress for selecting a specific word line in the memory cell block 110appointed by the block address, signals ‘BISH<0>’, ‘BISH<1>’, ‘BISL<0>’and ‘BISL<1>’ shift to a low level. Therefore, the upper-side andlower-side bit line isolation transistors of a corresponding senseamplifier are all disabled, and the bit lines are isolated from thesense amplifier. In this case, a selected word line <0> is enabled to ahigh level, and cell data are transferred to the bit lines throughcharge sharing. Herein, the word line <0> represents a first word lineof the memory cell block 110.

2) Activation of Memory Cell Block 112:

After a predetermined time period elapses, when an active command isinputted together with a block address for appointing the memory cellblock 112 and a row address for selecting a specific word line in thememory cell block 112 appointed by the block address, signals ‘BISH<2>’,‘BISH<3>’, ‘BISL<2>’ and ‘BISL<3>’ shift to a low level. Therefore, theupper-side and lower-side bit line isolation transistors of acorresponding sense amplifier are all disabled, and the bit lines areisolated from the sense amplifier. In this case, a selected word line<1024> is enabled to a high level, and cell data are transferred to thebit lines through charge sharing. Herein, the word line <1024>represents a first word line of the memory cell block 112.

3) Activation of Memory Cell Block 114:

When an active command is inputted together with a block address forappointing the memory cell block 114 and a row address for selecting aspecific word line in the memory cell block 114 appointed by the blockaddress, signals ‘BISH<4>’, ‘BISH<5>’, ‘BISL<4>’ and ‘BISL<5>’ shift toa low level. Therefore, the upper-side and lower-side bit line isolationtransistors of a corresponding sense amplifier are all disabled, and thebit lines are isolated from the sense amplifier. In this case, aselected word line <2048> is enabled to a high level, and cell data aretransferred to the bit lines through charge sharing. Herein, the wordline <2048> represents a first word line of the memory cell block 114.

4) Sensing of Memory Cell Block 110:

When a burst stop command ‘Bs’ is inputted from the exterior togetherwith a block address for appointing the memory cell block 110, signals‘BLEQ<0>’ and ‘BLEQ<1>’ shift to a low level. Therefore, transistorscontrolled by signals ‘BLEQ<0>’ and ‘BLEQ<1>’ are disabled. At the sametime, block switch transistors connecting the local input/output lines‘LIO’ and ‘/LIO’ and the main input/output lines ‘MIO’ and ‘/MIO’ areenabled by signal ‘/BLEQ’, thereby being in a ready state for a write orread operation. Then, signals ‘BISH<1>’ and ‘BISL<0>’ shift from a lowlevel to a high level, so that bit line isolation transistors aredisabled. As a result, the electric potential levels of the bit lines‘Bit’ and ‘/Bit’, to which charge has been shared, are transferred tothe sense amplifier. Then, signal ‘RTO’ for the sense amplifier isactivated to a high level and signal ‘SE’ for the sense amplifier isactivated to a low level, so that a voltage difference (AV) between thebit lines ‘Bit’ and ‘/Bit’ is sensed and amplified.

5) Write (or Read) of Memory Cell Block 110:

When a write command ‘Wt’ (or read command) is inputted together with acolumn address, an interior column address signal ‘Yi’ is generated (inthis case, signal ‘LIOPC’ shifts to a low level). Accordingly, data ofthe local input/output lines ‘LIO’ and ‘/LIO’, which have passed throughthe block switch transistors via the main input/output lines ‘MIO’ and‘/MIO’, are transferred to the bit lines connected to the senseamplifier. For reference, in the case of a read operation, when aninterior column address signal ‘Yi’ is enabled, data of bit lines havingbeen amplified by the sense amplifier are transferred to the maininput/output lines via the local input/output lines and the block switchtransistors.

6) Precharge of Memory Cell Block 110:

When a precharge command ‘Pcg’ is applied together with a block addressfor appointing the memory cell block 110, a word line ‘WL<0>’ shifts toa low level, and memory cell data are protected. Then, signals ‘BISH<0>’and ‘BISL<1>’, which have been in a low level, shift to a high level,thereby enabling the bit line isolation transistors to which the signals‘BISH<0>’ and ‘BISL<1>’ are inputted. Then, signals ‘BLEQ<0>’ and‘BLEQ<1>’ shift from a low level to a high level, thereby prechargingthe bit lines ‘Bit’ and ‘/Bit’ and the local input/output lines ‘LIO’and ‘/LIO’ to a voltage level of ‘VBLP’. At the same time, the blockswitch transistors connecting the local input/output lines ‘LIO’ and‘/LIO’ and the main input/output lines ‘MIO’ and ‘/MIO’ are disabled bysignal ‘/BLEQ’, thereby shutting off the transmission of the data.

7) Activation of Memory Cell Block 116:

When an active command is inputted together with a block address forappointing the memory cell block 116 and a row address for selecting aspecific word line in the memory cell block 116 appointed by the blockaddress, signals ‘BISH<6>’, ‘BISH<7>’, ‘BISL<6>’ and ‘BISL<7>’ shift toa low level. Accordingly, the upper-side and lower-side bit lineisolation transistors of a corresponding sense amplifier are alldisabled, and the bit lines are isolated from the sense amplifier. Inthis case, a selected word line <3072> is enabled to a high level, andcell data are transferred to the bit lines through charge sharing.Herein, the word line <3072> represents a first word line of the memorycell block 116.

8) Sensing of Memory Cell Block 112:

When a burst stop command ‘Bs’ is inputted from the exterior togetherwith a block address for appointing the memory cell block 112, signals‘BLEQ<2>’ and ‘BLEQ<3>’ shift to a low level. Therefore, transistorscontrolled by signals ‘BLEQ<2>’ and ‘BLEQ<3>’ are disabled. At the sametime, the block switch transistors connecting the. local input/outputlines ‘LIO’ and ‘/LIO’ and the main input/output lines ‘MIO’ and ‘/MIO’are enabled by signal ‘/BLEQ’, thereby being in a ready state for awrite or read operation. Thereafter, signals ‘BISH<3>’ and ‘BISL<2>’having been at a low level shift to a high level, so that correspondingbit line isolation transistors are disabled. As a result, the electricpotential levels of the bit lines ‘Bit’ and ‘/Bit’, to which charge hasbeen shared, are transferred to the sense amplifier. Then, signal ‘RTO’for the sense amplifier is activated to a high level and signal ‘SE’ forthe sense amplifier is activated to a low level, so that a voltagedifference (AV) between the bit lines ‘Bit’ and ‘/Bit’ is sensed andamplified.

9) Write (or Read) of Memory Cell Block 112:

When a write command ‘Wt’ (or read command ‘Rd’) is inputted togetherwith a column address, an interior column address signal ‘Yi’ isgenerated (In this case, signal ‘LIOPC’ shifts to a low level).Accordingly, data of the local input/output lines ‘LIO’ and ‘/LIO’,which have passed through the block switch transistors via the maininput/output lines ‘MIO’ and ‘/MIO’, are transferred to the bit linesconnected to the sense amplifier. For reference, in the case of a readoperation, when an interior column address signal ‘Yi’ is enabled, dataof bit lines having been amplified by the sense amplifier aretransferred to the main input/output lines via the local input/outputlines and the block switch transistors.

10) Precharge of Memory Cell Block 112:

When a precharge command ‘Pcg’ is applied together with a block addressfor appointing the memory cell block 112, a word line ‘WL<1024>’ shiftsto a low level to protect memory cell data. Then, signals ‘BISH<2>’ and‘BISL<3>’, which have been at a low level, shift to a high level,thereby enabling the bit line isolation transistors to which the signals‘BISH<2>’ and ‘BISL<3>’ are inputted. Thereafter, signals ‘BLEQ<2>’ and‘BLEQ<3>’ shift from low levels to high levels, thereby precharging thebit lines ‘Bit’ and ‘/Bit’ and the local input/output lines ‘LIO’ and‘/LIO’ to a voltage level of ‘VBLP’. At the same time, the block switchtransistors connecting the local input/output lines ‘LIO’ and ‘/LIO’ andthe main input/output lines ‘MIO’ and ‘/MIO’ are disabled by. signal‘/BLEQ’, thereby shutting off the transmission of the data.

11) Activation of Memory Cell Block 110:

When an active command ‘Act’ is inputted together with a block addressfor appointing the memory cell block 110 and a row address for selectinga specific word line in the memory cell block 110 appointed by the blockaddress, signals ‘BISH<0>’, ‘BISH<1>’, ‘BISL<0>’ and ‘BISL<1>’ shift toa low level. Therefore, the upper-side and lower-side bit line isolationtransistors of a corresponding sense amplifier are all disabled, and thebit lines are isolated from the sense amplifier. In this case, aselected word line <1> is enabled to a high level, and cell data aretransferred to the bit lines through charge sharing. Herein, the wordline <1> represents a second word line of the memory cell block 110.

12) Sensing of Memory Cell Block 114:

When a burst stop command ‘Bs’ is inputted from the exterior togetherwith a block address for appointing the memory cell block 114, signals‘BLEQ<4>’ and ‘BLEQ<5>’ shift to a low level. Therefore, transistorscontrolled by signals ‘BLEQ<4>’ and ‘BLEQ<5>’ are disabled. At the sametime, the block switch transistors connecting the local input/outputlines ‘LIO’ and ‘/LIO’ and the main input/output lines ‘MIO’ and ‘/MIO’are enabled by signal ‘/BLEQ’, thereby being in a ready state for awrite or read operation. Next, signals ‘BISH<5>’ and ‘BISL<4>’ havingbeen at a low level shift to a high level, so that corresponding bitline isolation transistors are disabled. As a result, the electricpotential levels of the bit lines ‘Bit’ and ‘/Bit’, to which charge hasbeen shared, are transferred to the sense amplifier. Then, signal ‘RTO’for the sense amplifier is activated to a high level and signal ‘SE’ forthe sense amplifier is activated to a low level, so that a voltagedifference (AV) between the bit lines ‘Bit’ and ‘/Bit’ is sensed andamplified.

13) Write (or Read) of Memory Cell Block 114:

When a write command ‘Wt’ (or read command ‘Rd’) is inputted togetherwith a column address, an interior column address signal ‘Yi’ isgenerated (In this case, signal ‘LIOPC’ shifts to a low level).Accordingly, data of the local input/output lines ‘LIO’ and ‘/LIO’,which have passed through the block switch transistors via the maininput/output lines ‘MIO’ and ‘/MIO’, are transferred to the bit linesconnected to the sense amplifier. For reference, in the case of a readoperation, when an interior column address signal ‘Yi’ is enabled, dataof bit lines having been amplified by the sense amplifier aretransferred to the main input/output lines via the local input/outputlines and the block switch transistors.

14) Precharge of Memory Cell Block 114:

When a precharge command ‘Pcg’ is applied together with a block addressfor appointing the memory cell block 114, a word line ‘WL<2048>’ shiftsto a low level to protect memory cell data. Then, signals ‘BISH<4>’ and‘BISL<5>’, which have been at a low level, shift to a high level,thereby enabling the bit line isolation transistors to which the signals‘BISH<4>’ and ‘BISL<5>’ are inputted. Next, signals ‘BLEQ<4>’ and‘BLEQ<5>’ shift from low levels to high levels, thereby precharging thebit lines ‘Bit’ and ‘/Bit’ and the local input/output lines ‘LIO’ and‘/LIO’ to a voltage level of ‘VBLP’. At the same time, the block switchtransistors connecting the local input/output lines ‘LIO’ and ‘/LIO’ andthe main input/output lines ‘MIO’ and ‘/MIO’ are disabled by signal‘/BLEQ’, thereby shutting off the transmission of the data.

When charge sharing time is kept for a very long period of time whilesequentially performing the above active ‘Act’, burst stop ‘Bs’, write‘Wt’ (or read ‘Rd’) and precharge ‘Pcg’ operations with respect toeven-numbered memory cell blocks in regular sequence (that is, in theinterleave scheme), it is possible to screen current leakage caused byPVT variation and defects in a memory cell. In addition, it is possibleto perform a write (or read) operation even while several memory blocksare being in an active state, so that the test time can be efficientlyreduced.

When the test of the even-numbered memory cell blocks 110, 112, 114 and116 has been finished, the active ‘Act’, burst stop ‘Bs’, write ‘Wt’ (orread ‘Rd’) and precharge ‘Pcg’ operations sequentially performed withrespect to the odd-numbered memory cell blocks 111, 113, 115 and 117with the interleave scheme in the same method as described above.

FIG. 3 is a waveform diagram for explaining the test method describedabove with reference to FIGS. 1 and 2 according to an embodiment of thepresent invention.

As shown in FIG. 3, it can be understood that an active operation isperformed for the first word line ‘WL<0>’ of the memory cell block 110,an active operation is performed for the first word line ‘WL<1024>’ ofthe memory cell block 112, and an active operation is performed for thefirst word line ‘WL<2048>’ of the memory cell block 114. That is, it canbe understood that active operations are performed in the interleavescheme. Thereafter, sense, write and precharge operations aresequentially performed for the memory cell block 110, and then sense,write and precharge operations are sequentially performed for the memorycell block 112. Next, an active operation is performed for the secondword line ‘WL<1>’ of the memory cell block 110; sense, write andprecharge operations are sequentially performed for the memory cellblock 114; and then an active operation is performed for the second wordline ‘WL<1025>’ of the memory cell block 112. Then, an active operationis performed for the second word line ‘WL<2049>’ of the memory cellblock 114. Thereafter, sense, write and precharge operations aresequentially performed for the memory cell block 110. For reference,‘YI’ in FIG. 3 represents an interior column address signal.

FIG. 4 is a waveform diagram illustrating the test method of the presentinvention by means of signals for the memory device, in which aprocedure of performing a write operation is shown. Therefore, FIG. 4may be considered as another waveform diagram of FIG. 3.

In FIG. 4, ‘CMD’ is an abbreviation of ‘command’, ‘CLK’ represents anexterior clock signal, ‘/CS’ represents a chip select signal, and ‘TM’represents that the test mode is on. ‘Add(blk)’ represents an addressfor appointing a memory cell block, ‘B0’ represents that the memory cellblock 110 is selected, ‘B2’ and ‘B4’ represent that the memory cellblocks 112 and 114 are selected, respectively. In addition, ‘DIN’represents that data are inputted. Finally, ‘Blk<0>’, ‘Blk<2>, ‘Blk<4>’and ‘Blk<6>’, shown in the lower portion of FIG. 4, represent memorycell blocks 110, 112, 114 and 116, respectively.

FIG. 5 is a waveform diagram illustrating the test method of the presentinvention by means of signals for the memory device, in which aprocedure of performing a read operation is shown. Compared with theprocedure for the write operation described with reference to FIG. 4,the procedure of the read operation shown in FIG. 5 is equal to that forthe write operation, except that a test is performed. For reference,‘DOUT’ represents that data are outputted.

As shown in FIGS. 4 and 5, a time period required to perform the active,sense, write (read) and precharge operations for a specific word line(e.g., WL<0> ) of a specific memory cell block (e.g., memory cell block110) is equal to that required to perform the same operations foranother word line of another memory cell block. That is, since it takesa time period of ‘11tCLK’ (herein, ‘tCLK’ is a period of ‘CLK’) toperform the active, sense, write (read) and precharge operations for theword line ‘WL<0>’ of the memory cell block 110, it also takes the timeperiod of ‘11tCLK’ to perform the active, sense, write (read) andprecharge operations for the word line ‘WL<1024>’ of the memory cellblock 112. Similarly, the same time period is required for the othercases.

As shown in FIGS. 4 and 5, when ‘4tCLK’ elapses after the first wordline ‘WL<0>’ of the memory cell block 110 is enabled, the first wordline ‘WL<1024>’ of the memory cell block 112 is enabled. Next, when‘4tCLK’ elapses after the first word line ‘WL<1024>’ of the memory cellblock 112 is enabled, the first word line ‘WL<2048>’ of the memory cellblock 114 is enabled. Then, when ‘4tCLK’ elapses after the first wordline ‘WL<2048>’ of the memory cell block 114 is enabled, the first wordline ‘WL<3072>’ of the memory cell block 116 is enabled. Next, when‘4tCLK’ elapses after the first word line ‘WL<3072>’ of the memory cellblock 116 is enabled, the second word line ‘WL<1>’ of the memory cellblock 110 is enabled. Then, when ‘4tCLK’ elapses after the second wordline ‘WL<1>’ of the memory cell block 110 is enabled, the second wordline ‘WL<1025>’ of the memory cell block 112 is enabled. Thereafter, thesame procedure is repeated. As shown in these drawings, the memory cellblocks are sequentially and circularly activated in a period of ‘4tCLK’,and each activated memory cell block is precharged when ‘11tCLK’ elapsesfrom its activated time point. Those skilled in the art will appreciatethat the above-mentioned test period can be adjusted based on the numberof memory cell blocks.

When the test procedure for the even-numbered memory cell blocks 110,112, 114 and 116 have been finished, the test for the odd-numberedmemory cell blocks 111, 113, 115 and 117 is performed in the same methodas described above.

According to the present invention, as shown in FIGS. 1 and 2, since asense amplifier is connected between an upper memory cell block (or cellmatrix) and a lower memory cell block, the test is separately performedwith respect to the even-numbered memory cell blocks and theodd-numbered memory cell blocks, respectively. However, in the case oftesting a memory device in which memory cell blocks correspondone-to-one with sense amplifiers, it does not need to separate theeven-numbered memory cell blocks and the odd-numbered memory cellblocks. Therefore, in this case, all the memory cell blocks can betested in regular sequence.

In addition, although the embodiment of the present invention isdescribed with respect to the method for first testing the even-numberedmemory cell blocks and then testing the odd-numbered memory cell blocks,the above-mentioned procedure may be applied to a method for firsttesting the odd-numbered memory cell blocks and then testing theeven-numbered memory cell blocks. In this case, the same test method asdescribed above may be applied, except that the test sequence isreversed, so description thereof will be omitted.

The conventional method for testing a plurality of memory cell blocks isperformed one after another in regular sequence in such a manner thatwhen the test for one memory cell block has been finished, the test foranother memory cell block is performed, so that a very long test periodis required. However, according to an embodiment of the presentinvention, while the test operation for one memory cell block is beingperformed, test operations for multiple other memory cell blocks can beperformed, so that it is possible to significantly reduce the total testtime.

Although a preferred embodiment of the present invention has beendescribed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible without departing from the scope and spirit of the invention asdisclosed in the accompanying claims.

1. A method for testing a memory device provided with a bank whichincludes a plurality of memory cell blocks, the method comprising thesteps of: a) enabling a test mode signal; b) activating one of thememory cell blocks and then activating other memory cell blocks one byone in a predetermined time period corresponding to enabling of the testmode signal; and c) performing sense, read (or write) and prechargeoperations for an activated memory cell block from among the memory cellblocks.
 2. The method as claimed in claim 1, wherein the active, sense,read and precharge operations are performed by commands applied from anexterior of the memory device.
 3. The method as claimed in claim 1,wherein the active, sense, read and precharge operations are performedsequentially for a plurality of word lines included in each of thememory cell blocks.
 4. The method as claimed in claim 1, wherein, whensense, read (or write) and precharge operations for one of the memorycell blocks have been finished through step c), one of remaining memorycell blocks is activated.
 5. A method for testing a memory deviceprovided with a bank which includes N number of memory cell blocks andsense amplifiers located between the memory cell blocks, the methodcomprising the steps of: a) enabling a test mode signal; b) expressingthe N memory cell blocks as a first, a second, . . . , an Nth (herein,‘N’ is a natural number exceeding ‘three’) memory cell block; c)activating one of odd-numbered (first, third, fifth, . . . ) memory cellblocks from among the N memory cell blocks, and then activatingremaining odd-numbered memory cell blocks one by one in a predeterminedtime period corresponding to enabling of the test mode signal; d)performing sense, read (or write) and precharge operations for eachactivated memory cell block from among the odd-numbered memory cellblocks; and e) performing steps b) to d) for even-numbered memory cellblocks after tests for all the odd-numbered memory cell blocks have beenfinished.
 6. The method as claimed in claim 5, wherein the active,sense, read and precharge operations are performed sequentially for aplurality of word lines included in each of the N memory cell blocks. 7.The method as claimed in claim 5, wherein, when the sense, read (orwrite) and precharge operations for one of the odd-numbered memory cellblocks have been finished through step d), one of remaining odd-numberedmemory cell blocks is activated; and when the sense, read (or write) andprecharge operations for one of the even-numbered memory cell blockshave been finished through step e), one of remaining even-numberedmemory cell blocks is activated.
 8. A method for testing a memory deviceprovided with a bank which includes N number of memory cell blocks andsense amplifiers located between the memory cell blocks, the methodcomprising the steps of: a) enabling a test mode signal; b) expressingthe N memory cell blocks as a first, a second, . . . , an Nth (herein,‘N’ is a natural number exceeding ‘three’) memory cell block; c)activating one of even-numbered (second, fourth, sixth, . . . ) memorycell blocks from among the N memory cell blocks, and then activatingremaining even-numbered memory cell blocks one by one in a predeterminedtime period corresponding to enabling of the test mode; d) performingsense, read (or write) and precharge operations for each activatedmemory cell block from among the even-numbered memory cell blocks; ande) performing steps b) to d) for odd-numbered (first, third, fifth, . .. ) memory cell blocks after tests for all the even-numbered memory cellblocks have been finished.
 9. The method as claimed in claim 8, whereinthe active, sense, read and precharge operations are performedsequentially for a plurality of word lines included in each of the Nmemory cell blocks.
 10. The method as claimed in claim 8, wherein, whenthe sense, read (or write) and precharge operations for one of theeven-numbered memory cell blocks have been finished through step d), oneof remaining even-numbered memory cell blocks is activated; and when thesense, read (or write) and precharge operations for one of theodd-numbered memory cell blocks have been finished through step e), oneof remaining odd-numbered memory cell blocks is activated.